1. Field of the Invention
The present invention relates to a polishing pad and a method for making the same, and more particularly to a conductive polishing pad and a method for making the same.
2. Description of the Related Art
FIG. 1 shows a schematic view of an application of a conventional conductive polishing pad disclosed in Taiwan (R.O.C.) Patent Publication No. 200505632. The conductive polishing pad 1 comprises a bottom layer 11 and a polishing layer 12. The bottom layer 11 has a circuit 111. The polishing layer 12 has a polishing surface 121, and the polishing surface 121 has at least one anode 122 and at least one cathode 123. The anode 122 and the cathode 123 are connected to a positive terminal 221 and a negative terminal 222 of a power outlet 22 respectively by the circuit 111 and an electrical connector 21.
During polishing, the conductive polishing pad 1 is fixed on a polishing disc 23, and a substrate 24 is fixed on a substrate carrier 25. The substrate 24 has a metal layer 241, and is disposed over the polishing surface 121. A slurry 26 is disposed between the substrate 24 and the polishing surface 121. When the power outlet 22 is on, and the slurry 26, the anode 122, the cathode 123 and the metal layer 241 of the substrate 24 contact one another, a short circuit is formed. First, the charge of the metal atoms of the metal layer 241 is transferred, and metal ions are formed (M→M++e−) and gather on the surface of the substrate 24. Afterward, an acceptor (complexing agent in the slurry 26) is diffused to the surface of the metal layer 241, and complexes are formed between the acceptor and the metal ions. Finally, the complexes are diffused from the surface of the metal layer 241 into the slurry 26. The diffusion rates of the complexes on the protrusion and the concavity on the surface of the substrate 24 are different. The complexes diffuse faster on the protrusion than on the concavity, and thus, a smooth surface on substrate 24 is formed.
The conventional conductive polishing pad 1 has the following disadvantages. The material of the anode 122 and the cathode 123 is metal with high hardness, so the surface of the substrate 24 will be scratched easily during polishing. Moreover, the anode 122 and the cathode 123 are worn after electrochemical mechanical polishing, and thus, the polishing surface 121 becomes rough, and the yield rate is reduced.
Therefore, it is necessary to provide a conductive polishing pad and a method for making the same to solve the above problems.